It is known for using solar energy to employ fixed solar cells constituting thermal converters, also called "thermal function insolators" and hereinafter designated as "insolators". The latter generally comprise:
A transparent front covering through which solar radiation or incident light penetrates;
Absorbent receiving surfaces which convert the energy from the solar radiation into heat which is then transferred to heat transfer fluids, gases, or various liquids, in particular, air or water;
A rear thermal insulation covering.
The transparent covering which is mainly used for protection of the inside of the apparatus from bad weather is often designed and constructed so as to reduce thermal losses caused by transmission to the outside of the thermal flux generated in the apparatus, and also to oppose the passage of convective currents either from the inside of the apparatus or from the outside thereof.
Moreover, the interval also called "intermediate space" between such transparent covering and the absorbent receiving surfaces is generally of a small thickness so as to reduce the inner convective currents which may be responsible for significant thermal losses. This is why heretofore various devices were placed in such intermediate space for specifically combatting such convective currents and also the transmission of the infrared radiation coming from the heated surfaces, without however giving complete satisfaction as regards total utilization of incident energy